1. Field of the Invention
This invention relates to a process for optimizing the ignition advance of an internal combustion engine.
2. Description of the Prior Art
U.S. Pat. No. 4,268,910 describes a process for optimizing the ignition advance of an internal combustion engine equipped with a computer containing a programmed law for ignition advance as a function of the speed and the load of the engine and for a system for detecting pinging which supplies data representative of the presence or absence of pinging at each engine stroke, according to which there are determined, as a function of the speed and the load of the engine, at least two operating zones, namely a critical zone and a noncritical zone. When pinging is detected in the critical zone, the ignition advance generated for at least one of the following engine strokes is delayed. The process makes it possible to avoid the correction as a function of the pinging taking place regardless of the load and the speed of the engine. Thus, for example, if a pinging stroke appears and is corrected at full load (critical zone) and if the full load is released before the return to the programmed law, to return to partial load (noncritical zone), correction is no longer made and the programmed law for ignition advance corresponding to the supply of the maximum torque of the engine for the speed and the load under consideration is immediately resumed.
However, this process does not make it possible, in the critical zone where the risk of pinging is greatest, to avoid a return to the programmed advance that is too fast. Now if, under certain operating conditions of the engine, this programmed advance is near or coincides with the pinging limit, which can be the case as the engine ages, there will be a new pinging stroke each time the angle of advance returns to the initial law. If these pinging strokes are too numerous, then there is risk of damaging the engine.
In an attempt to solve this problem, the U.S. Pat. No. 4,233,944 describes a process according to which, after a pinging stroke, the advance is delayed and this delay is maintained longer the more stable are the operating conditions of the engine. On the other hand, the programmed advance is returned to short time operation as soon as the engine operates during transient operating conditions. However, this solution is not satisfactory either because the protection of the engine is poorly assured during the transient operations, some of which exhibit high risks of pinging.